The present disclosure relates to protective coatings for substrates. In particular, the present disclosure relates to protective coatings for use in self-cleaning systems.
Coated surfaces, such as painted surfaces, often accumulate dirt and dust with time, particularly when exposed to the environment. This is a particular issue for such architectural building products as painted steel sheet which is, for example, used in roof and wall cladding. As a result, these surfaces have to be periodically cleaned to maintain their appearance. The cleaning process is typically costly, time consuming and sometimes difficult, particularly when these surfaces are hard to access. A significant amount of this dirt and dust is comprised of organic material.
In this regard, there is a need to reduce organic material accumulation on the coated surface to avoid the need to manually clean the coated surfaces regularly.
One solution is to include a substance in the coating that can degrade the organic material. One method of degrading organic material is to incorporate a photocatalytic layer in a coating surface. Under the action of light, the photocatalytic layer produces reactive oxygen species, such as hydroxyl and superoxide ions, that react with and destroy organic material. However, these ions can also attack the underlying substrate, if it includes an organic composition (such as a paint layer), and can therefore adversely affect the durability and longevity of the coating.
Accordingly, there is a need for a means to impede diffusion of these reactive oxygen species.
The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the apparatus and method as disclosed herein.